Enhanced antibacterial activity of silica nanorattles with ZnO combination nanoparticles against methicillin-resistant Staphylococcus aureus

Green Derived Zinc Oxide (ZnO) for the Degradation of Dyes from Wastewater and Their Antimicrobial Activity: A Review

The quest for eco-friendly synthetic routes that can be used for the development of multifunctional materials, in particular for water treatment, has reinforced the use of plant extracts as replacement solvents in their use as reducing and capping agents during the synthesis of green derived materials. Amongst the various nanoparticles, Zinc Oxide (ZnO) has emerged as one of the preferred candidates for photocatalysis due to its optical properties. Moreover, ZnO has also been reported to possess antimicrobial properties against various bacterial strains such as E. coli and S. aureus. In this review, various types of pollutants including organic dyes and natural pollutants are discussed. The treatment methods that are used to purify wastewater with their limitations are highlighted. The distinguishing properties of ZnO are clearly outlined and defined, not to mention the performance of ZnO as a green derived photocatalyst and an antimicrobial agent, as well. Lastly, an overview is given of the challenges and possible further perspectives.

Nanomaterial-Based Zinc Ion Interference Therapy to Combat Bacterial Infections

Pathogenic bacterial infections are the second highest cause of death worldwide and bring severe challenges to public healthcare. Antibiotic resistance makes it urgent to explore new antibacterial therapy. As an essential metal element in both humans and bacteria, zinc ions have various physiological and biochemical functions. They can stabilize the folded conformation of metalloproteins and participate in critical biochemical reactions, including DNA replication, transcription, translation, and signal transduction. Therefore, zinc deficiency would impair bacterial activity and inhibit the growth of bacteria. Interestingly, excess zinc ions also could cause oxidative stress to damage DNA, proteins, and lipids by inhibiting the function of respiratory enzymes to promote the formation of free radicals. Such dual characteristics endow zinc ions with unparalleled advantages in the direction of antibacterial therapy. Based on the fascinating features of zinc ions, nanomaterial-based zinc ion interference therapy emerges relying on the outstanding benefits of nanomaterials. Zinc ion interference therapy is divided into two classes: zinc overloading and zinc deprivation. In this review, we summarized the recent innovative zinc ion interference strategy for the treatment of bacterial infections and focused on analyzing the antibacterial mechanism of zinc overloading and zinc deprivation. Finally, we discuss the current limitations of zinc ion interference antibacterial therapy and put forward problems of clinical translation for zinc ion interference antibacterial therapy.

Tri-functional SERS nanoplatform with tunable plasmonic property for synergistic antibacterial activity and antibacterial process monitoring

Strategies integrating synergistic high-efficiency bacterial killing and antibacterial process monitoring capability are desirable. Herein, a tri-functional surface-enhanced Raman spectroscopy (SERS) nanoplatform, namely 4-mercaptobenzoic acid-encoded gold nanorods@silver coated with a layer of bovine serum albumin (AuNRs@Ag@4-MBA@BSA), with excellent biocompatibility, stability, tunable plasmonic property and activatable photothermal effect is introduced for Ag⁺/photothermal therapy (PTT) synergistic antibacterial activity and antibacterial process monitoring. An exogenous etchant is used to controllably model the physiological process of metallic silver biodegradation. Ag shell etching causes the surface plasmon resonance band of SERS nanotags to red-shift to near-infrared region, activates the photothermal conversion capability, and triggers PTT, which in turn accelerates Ag shell etching. The antibacterial rates for Staphylococcus aureus and Escherichia coli after 10 min treatment can achieve 99.5% and 99.9%, respectively. Furthermore, the near-field effect and ultrasensitive property render the SERS intensity decrease ratio is dependent on Ag shell etching as well as temperature rising and thus relevant to antibacterial activity. We have demonstrated a strong correlation between SERS signal and antibacterial effect, and have verified the possibility of antibacterial process monitoring in vitro using SERS-based methodology. We envision that our integrated strategy being used for in vivo high-efficiency bacterial killing and antibacterial process monitoring.

Methotrexate-loaded folic acid of solid-phase synthesis conjugated gold nanoparticles targeted treatment for rheumatoid arthritis

PURPOSE

Methotrexate (MTX) is a first-line drug for rheumatoid arthritis (RA). Targeting of MTX to inflamed joints is essential to the prevention of potential toxicity and improving therapeutic effects. Gold nanoparticles (GNPs) are characterized by controllable particle sizes and good biocompatibilities, therefore, they are promising drug delivery systems. We aimed at developing a GNPs drug delivery system incorporating MTX and folic acid (FA) with strong efficacies against RA.

METHODS

MTX-Cys-FA was synthesized through solid-phase organic synthesis. Then, it was coupled with sulfhydryl groups in GNPs, thereby successfully preparing a GNPs/MTX-Cys-FA nanoconjugate with targeting properties. Physical and chemical techniques were used to characterize it. Moreover, we conducted its stability, release, pharmacokinetics, biodistribution and cell cytotoxicity, cell uptake, cell migration, as well as its therapeutic effect on CIA rats. The histopathology was conducted to investigate anti-RA effects of GNPs/MTX-Cys-FA nanoconjugates.

RESULTS

The GNPs/MTX-Cys-FA nanoconjugate exhibited a spherical appearance, had a particle size of 103.06 nm, a zeta potential of -33.68 mV, drug loading capacity of 11.04 %, and an encapsulation efficiency of 73.61%. Cytotoxicity experiments revealed that GNPs had good biocompatibilities while GNPs/MTX-Cys-FA exhibited excellent drug-delivery abilities. Cell uptake and migration experiment showed that nanoconjugates containing FA by LPS activated mouse mononuclear macrophages (RAW264.7) was significantly increased, and they exerted significant inhibitory effects on human fibroblast-like synoviocytes (HFLS) of RA (p<0.01). In addition, the nanoconjugate prolonged blood circulation time of MTX in collagen-induced arthritis (CIA) rats (p<0.01), enhanced MTX accumulation in inflamed joints (p<0.01), enhanced their therapeutic effects (p<0.01), and reduced toxicity to major organs (p<0.01).

CONCLUSION

GNPs/MTX-Cys-FA nanoconjugates provide effective approaches for RA targeted therapeutic strategies.

Antibacterial applications of graphene oxides: structure-activity relationships, molecular initiating events and biosafety

Bacterial infections may lead to diverse acute or chronic diseases (e.g., inflammation, sepsis and cancer). New antibiotics against bacteria are rarely discovered in recent years, which necessitates the exploration of new antibacterial agents. Engineered nanomaterials (ENMs) have been extensively studied for antibacterial use because of their long lasting killing effects in wide spectra of bacteria. Graphene oxide (GO) is one of the most widely studied ENMs and exhibit strong bactericidal effects. The physicochemical properties of GO play important roles in bacterial killing by triggering a cascade of toxic events. Many studies have explored the signaling pathways of GO in bacteria. Although molecular initiating events (MIEs) of GO in bacteria dominate its killing efficiency as well as toxicity mechanisms, they have been rarely reviewed. In this report, we discussed the structure-activity relationships (SARs) involved in GO-induced bacterial killing and the MIEs including redox reaction with biomolecules, mechanical destruction of membranes and catalysis of extracellular metabolites. Furthermore, we summarized the clinical or commercial applications of GO-based antibacterial products and discussed their biosafety in mammal. Finally, we reviewed the remaining challenges in GO for antibacterial applications, which may offer new insights for the development of nano antibacterial studies.